TWENTIETH- - Synapse Music

Timbre and Texture: Electronic 253
sound at a regular rate. Phase vocoding changes the playback rate of these "frames" of
sound. Roger Reynold's Transfigured Wind IV (1985) for flute, and digital audio, uses
phase vocoding to alter recordings of flute gestures, which are then played back as accompaniment
to a li ve fluti st.
Convolution is a type of cross synthesis, which takes the frequency characteristics
of one sound and applies them to the frequency characteristic of another sound. The mathematical
process involves multiplication of frequencies, which means that frequencies present
in both sounds will be enhanced, while frequencies present in only onc sound will be
eliminated. In one respect, it can be thought of as using onc sound to filter another sound.
Other analysis/resynthesis techniques exist and have been used to good musical results.
lonathan Harvey's Mortuos Plango, Vivos Voco (1981) uses an analysis of a large
church bell applied to the recording of a boy's voice. The effect is one of a merged boy and
bell that produces unique and haunting textures. Paul Lansky's Idle Chatter (1985) takes
analyzed vocal sounds and separates the more static portions from the fast-changing transients
(the vowels from the consonants, plosives. and sibilance) to create a rhythmic chorus
of nonsense vocal sounds.
The affordability, power, and versatility of this technology have led. to a resurgence
of interest and compositional activity in the area of concrete music. Composers are able to
alter concrete sound sources digitally to create rich textures more easily and quickJy than
with tape, and there is no loss of signal quality (or added noise) like that associated with
analog techniques.
THE DEVELOPMENT OF MIDI
While early programming languages required massive mainframe computers to synthesize
sound (making access to them very limited) many composers today work with a variety of
open-ended systems and premade systems on personal computers that provide far greater
processing power than those earlier mainframes.
Most premade applications trace their history to the development of the MIDI (Musical
Instrument Digital Interface) specification in the early 1980s. MIDI is a digital communication
standard (or language) designed originally to allow the synthesizers of one
manufacturer to transmit performance instructions (such as, "now playa C4, now stop playing
that C4") to synthesizers made by another manufacturer. MIDI made it easily possible
for computers to store and communicate performance instructions, and led to the development
of sequencing programs that allowed composers to organize and edit computer music
scores in more musically intuitive ways than afforded by early programming languages.
Despite MIDI's weaknesses (slow communication speed between devices, limited
resolution of control values, and control parameters defined by keyboard performance
only) the specification has remained largely unchanged since its inception. Even today, almost
all new computer music synthesis programs (premade or open-ended) use MIDI as
the basis for controlling parameters and communicating between applications. MIDI
breaks down most of the common keyboard-based performance actions into a stream of
bits (the smallest unit of binary data, I or O-on or off) arranged in groups of eight to form
a byte. Usually two to three bytes are arranged to form a single MIDI message, with seven